Two pipe steam, no vents, no traps.

Dadministrator

I'm looking at a two pipe steam system with no vents or traps anywhere in the system. Supplys come off the main into the tops of the radiators and returns come out the bottom (no trap) and into the return pipe. The supply and return drop down and join together at the end of the run at a point about two feet off the floor. The return pitches back and directly into the boiler with no Hartford loop. All controls and feeders are standard. The house was just purchased with a non working boiler and no user history. The boiler is way over the house load.
I only know enough about steam to know that none of this is normal., I am concerned about any possible caveats when re[lacing the boiler.

Ironman

Can you post some pics of the boiler, the piping, and rads?

Dadministrator

I can draw a diagram. Nothing unique about the rads. The boiler is a Peerless 61 series.

Jamie Hall

Almost certainly is -- or was -- a vapour system. The lack of traps is not so odd; the steam flow to the radiators may have been controlled by orifices or adjustable valves, or the outflow from the radiators may have been controlled by any one of a variety of weird contraptions which look like elbows, but aren't.

The lack of a vent is odd, however. The most likely place for them to have been one is at or near the end of the dry return, just before it turns down to join the wet return Look around.

You do say that the supplys for the radiators come off the return. That is also odd, to put it mildly... I would expect the supplies off a steam main, and the returns into an independent dry return -- and, depending on how the whole thing is piped, some wet returns as well. If there are independent steam mains, they should also be vented -- but there were a variety of ways to do that.

There are two major things to look for replacing the boiler, besides the obvious one to get the correct size. The first is water line elevation: it must match the old one as closely as possible. Do what you need to do to do that. The second is control. If this really was a vapour system as I expect, if needs to have a vapourstat for control, probably set to cutout at about 10 ounces.

Ironman

Pics would show the particular components of the system (or the lack of them).
It's easy to post them from a smart phone, tablet, etc.

Dadministrator

I corrected that error Jamie. Multi Tasking. Providing tech support, on hold for parts, roofer is here...
There are valves at each radiator supply.
My thoughts here are that with no vents (and there are NONE) the system will create some vacuum as the steam collapses.
Also there is no real wet return. the return comes along the ceiling and drops right into the low point of the water jacket on the side of the boiler. And again the supply and return drop down at the end of the run and join together about 26" from the floor.
The operating controls are standard pressuretrol, LWCO with blow down and electric feed.

BobC

We cannot see what you are looking at, somebody may spot something that will yield a clue. Without pictures it's all just spit balling.

Bob

jumper

Sounds somewhat like those old multi-residential in Toronto I've described in this conference. Even with only one pipe riser the terminals were connected twice,top and bottom. No vents. Instead there was a vacuum generator in the boiler room to periodically evacuate air from the system. Generally a water powered venturi eductor in those days when water was inexpensive and pressure was high.

Those buildings had built in convectors but I suppose radiators would have worked better. The installer hoped other contractors would use his system so that he could sell the convectors. Didn't happen. But I think that as late as the seventies some small commercial & industrial buildings hooked up unit heaters that way. Using only one pipe! Certainly against installation manuals.

Those systems worked okay so long nobody knuckle headed them.

Dadministrator

Dadministrator

This is the best that I can do for a pic. If I get back in at some point ill snap a few. After speaking with a boiler company rep I was advised to not change ANYTHING. he said if the boiler is oversized leave it that way unless I can get someone who understands how this system works, or why it works.
Another estimator was oblivious to it even being a two pipe system, let alone its other idiosyncrasies.

Jamie Hall

Ah! Nice picture! Thank you. Which way do those mains and returns pitch? I hope towards the boiler...

That pipe that drops back down and then back up is a loop seal; it allows condensate from the far end of the steam main to get over to the dry return and get back to the boiler, but it will prevent steam from getting into the return -- provided the pressure is kept low. So that's important.

It's also important that there be vents at the ends of the steam mains, near that loop seal, and at the end of the dry return, near the boiler. You need both sets of vents for the thing to work well.

When you get around to pictures, a close up of the valves going into the radiators and of the elbows on the returns would help a lot in trying to identify what this was...

Dadministrator

There are no vents. Went back to look for them but there never have been vents. No tapping either.
And yes, all piping pitches back to the boiler. I did not show this in my artwork for aesthetic reasons.

A return visit revealed that the supply pitches downhill very slightly from the boiler to the end of the run. The return has a more obvious pitch to the boiler.

jumper

Has to be a way to get air out of supply main. Those Toronto systems had no loop seal so air could be exhausted somewhere on return or at boiler feed.

Dadministrator

I'm going to size this equal to the steam output of the old boiler. its huge for the house, but I don't want to upset the balance of the system.

Danny Scully

@Dadministrator, that's a terrible idea. I don't mean to be rude, but you really shouldn't be bidding on this job. Honestly, if you bid on this job you will be putting yourself, and the customer at financial risk. I don't mean to discourage you from learning about steam, but there is a lot to know. Start by reading (cover to cover) The Lost Art Of Steam Heat, which is sold right here.

Steamhead

That's a Tudor system. Go here for more:

https://heatinghelp.com/heating-museum/european-heating-systems-circa-1907/

There has to be a vent somewhere if the system is to work properly. It's probably somewhere on the return line near the boiler.

However, I have heard of these systems heating up partially without a vent, in which case the steam pressure would be running high enough to compress enough air so some steam could reach the radiators. But this is NOT how it's supposed to work!

Where are you located?

Dadministrator

You mean this old thing? Thanks for the warning, but I've been at this long enough to know this is an odd duck. After speaking with boiler company reps and tech support from too many companies to name I took what I think is the best advice. I was told to add traps, vents, condensate pumps etc. But I had a few tell me not to tinker with the system. I agree with that. It was designed to work, it used to work, and it should still work.
The new boiler has the same steam capacity as the 25 year old rust bucket and doesn't compromise our A dimension.
Unless of course he agrees to a hot water conversion.

Danny Scully

That's the one! @Dadministrator, you measured all the radiators and have a total edr?

KC_Jones

Sizing it to the old one is just flat out wrong, it might be right it might not. Doing it from the old is throwing darts. Don't do it.

Did you check for orifices?

Steamhead

Dadministrator said:

Unless of course he agrees to a hot water conversion.

I wouldn't push this unless you like living dangerously.

Dadministrator

Thanks Steamhead. Its been about ten years since I visited this site but I remember you being knowledgeable and helpful back then, and some one named Maddog I think.
Anyway I wouldn't normally look for a vent near the return. If it were there I would have seen it, but there may be a tapping. It does make perfect sense though that that's where it should be.
Ill look tomorrow. Thanks again, Ill let you know what I find.

As for EDR, if you gotta know Danny, it translates to a bit over 100,000 btus which is a bit over twice the house load and places us between two boiler sizes, closer to the smaller. I'm not at the office so I don't have the exact numbers but over 400. 430 maybe.

Dadministrator

That's it on page 208, steamhead. Very exciting to see that. This does not have the standpipes or whatever they are in the picture here, but the piping is exact otherwise. Does the tudor system use orifices on the supply to the radiator?

Steamhead

Yes. Many times these were shutters or other devices built into the shutoff valves. Dan mentions this in chapter 15 but we weren't aware of Frederic Tudor then.

Dadministrator

The Studor diagram is spot on except for the smaller pipes. I did find a vent at the end of the returns that ties into a cast iron plumbing vent in the attic.

Jamie Hall

Dadministrator said:

The Studor diagram is spot on except for the smaller pipes. I did find a vent at the end of the returns that ties into a cast iron plumbing vent in the attic.

Tally ho! Now if you can get the pressure right and hope that the rest of the fittings and valves are as they should be...

If you want to be really cautious, though, you could put a couple of big mouths on there.

Danny Scully

Yea I would remove that connection from the plumbing vent system.

jumper

Upstream of the loop seal needs some vent as well. At least I think so.

Jamie Hall

jumper said:

Upstream of the loop seal needs some vent as well. At least I think so.

Agreed. Odd it's there, but there it is...

Dadministrator

So everything is working beautifully. Thanks for the information Steamhead. Understanding the system enabled me to confidently round down from the load rather than up to the existing size. We swapped out the probe type LWCO with a No. 67. The vent pipe stayed cool so no steam is escaping the system. We had one radiator not working due to a valve stuck closed. We replaced that a few days later and throttled back until we were just heating the radiator. The old valve had no restrictor in it. After running a few days the boiler got noisy but skimming and removing sludge from the return quieted it down. I'm giving it a few weeks before skimming again and replacing the vent through the roof with a pair of steam vents in the basement.
Thanks again.

Steamhead

Glad we could help.

Fizz

Kudos to how this discussion was handled from Dadministrator to posters. In the end the winner was and is the home owner!